1. Technical Field
The present invention relates, in general, to the biodegradation of halogenated aliphatic hydrocarbons, and in particular, to the biodegradation of trichloroethylene.
2. Background Information
The halogenated aliphatic hydrocarbon trichloroethylene (TCE) is a volatile, chlorinated compound of increasing concern as a groundwater contaminate. TCE is potentially carcinogenic and is resistant to biological or abiological decomposition in subsurface waters. Conventional water treatment processes have been found to be ineffective in removing TCE from ground-water. Results obtained with aeration and adsorption to granular activited charcoal or Ambersorb resin, however, are more encouraging.
The TCE degradation potential of microbes found in groundwater systems has been examined. Evidence of anaerobic biodegradation has been reported, but the products of degradation include equally harmful metabolites, such as dichloroethylenes and vinyl chloride. Several studies suggest that TCE may be degraded under methanogenic conditions. Complete mineralization of TCE was obtained when nonsterile solids were exposed to natural gas in air, suggesting that methanotrophic microorganisms are capable of degrading TCE. A possible mechanism for the degradation of TCE by methanotrophs involves epoxidation of TCE by methane monooxygenase followed by transport of the epoxide out of the cell. In the aqueous extracellular environment, the TCE epoxide would be subject to rapid rearrangment yielding dichloroacetic acid, formate, and carbon monoxide, each of which would then be further degraded. All reports of TCE metabolism have involved the use of undefined, mixed populations of microorganisms. No pure cultures of methanotrophs have been reported to degrade TCE.
It is an object of the present invention to provide a method for the biodegradation of halogenated aliphatic hydrocarbons.
It is another object of the invention to provide a method for the complete mineralization of halogenated aliphatic hydrocarbons.
It is a further object of the invention to provide a process for isolating microorganisms capable of degrading halogenated aliphatic hydrocarbons.
It is another object of the invention to provide pure cultures of microorganisms capable of degrading halogenated aliphatic hydrocarbons.
Further objects and advantages of the present invention will be apparent from the discussion which follows.